<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .father{
            color:red;
            width:400px;
            height:100px;
            border:1px solid red;
        }
        .son{
            width:400px;
            height:50px;
            color:blue;
            border:1px solid blue;
        }
    </style>
</head>
<body>
    <!-- unset：去掉当前标签自己的样式如果样式可以继承就继承 -->
    <div class="father">
        <div class="son" style="color:unset;border:unset;">123</div>
    </div>
</body>
</html>